Solar cell apparatus

ABSTRACT

Disclosed is a solar cell apparatus. The solar cell apparatus includes a first solar cell; and a second solar cell partially overlapping with the first solar cell and connected to the first solar cell.

TECHNICAL FIELD

The embodiment relates to a solar cell apparatus.

BACKGROUND ART

Recently, as energy consumption is increased, a solar cell has beendeveloped to convert solar energy into electrical energy.

In particular, a CIGS-based cell, which is a PN hetero junctionapparatus having a substrate structure including a glass substrate, ametallic back electrode layer, a P type CIGS-based light absorbinglayer, a high resistance buffer layer, and an N type window layer, hasbeen extensively used.

Especially, the solar cell includes a plurality of cells connected toeach other in series and/or in parallel, and the characteristics of asolar cell apparatus may vary depending on the characteristics of thecells.

DISCLOSURE Technical Problem

The embodiment provides a solar cell apparatus which can be easilymanufactured, has improved efficiency, and is flexible.

Technical Solution

According to the embodiment, there is provided a solar cell apparatusincluding a first solar cell; and a second solar cell partiallyoverlapping with the first solar cell and connected to the first solarcell.

According to the embodiment, there is provided a solar cell apparatusincluding an insulating substrate, a first solar cell above theinsulating substrate, and a second solar cell having a portioninterposed between the insulating substrate and the first solar cellwhile being connected to a bottom surface of the first solar cell.

According to the embodiment, there is provided a solar cell apparatusincluding a first solar cell, a second solar cell connected to the firstsolar cell, and a connection member connecting the first solar cell tothe second solar cell. The connection member includes conductivepolymer.

Advantageous Effects

In the solar cell apparatus according to the embodiment, a plurality ofsolar cells are connected to each other while being overlapped with eachother. Accordingly, the solar cell apparatus according to the embodimentcan be formed without a patterning process to distinguish the solarcells from each other and connect the solar cells to each other.

Therefore, the solar cell apparatus according to the embodiment can beeasily manufactured.

In addition, in the solar cell apparatus according to the embodiment,the overlap region between the solar cells can be minimized. Further,the overlap region is an active region to convert the sun light intoelectrical energy.

Accordingly, the solar cell apparatus according to the embodiment hasimproved power generation efficiency.

In addition, the solar cells and the support substrate including aninsulator below the solar cells may be flexible. Therefore, the solarcell apparatus according to the embodiment is flexible.

In particular, when the connection member includes conductive polymer,the connection member can effectively connect the solar cells to eachother.

Therefore, the solar cell apparatus according to the embodiment may haveimproved electrical characteristics.

DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view showing a solar cell apparatus according to theembodiment;

FIG. 2 is a sectional view showing a solar cell;

FIG. 3 is a graph showing the composition of group I elements as afunction of a height in a light absorbing layer;

FIG. 4 is a sectional view taken along line A-A′ of FIG. 1;

FIGS. 5 to 8 are sectional views showing a method of manufacturing solarcells; and

FIGS. 9 and 10 are sectional views showing the manufacturing procedureof forming a light absorbing layer according to another embodiment.

BEST MODE Mode for Invention

In the description of the embodiments, it will be understood that, whena layer (or film), a region, a pattern, or a structure is referred to asbeing “on” or “under” another substrate, another layer (or film),another region, another pad, or another pattern, it can be “directly” or“indirectly” on the other substrate, layer (or film), region, pad, orpattern, or one or more intervening layers may also be present. Such aposition of the layer has been described with reference to the drawings.The thickness and size of each layer shown in the drawings may beexaggerated, omitted or schematically drawn for the purpose ofconvenience or clarity. In addition, the size of elements does notutterly reflect an actual size.

FIG. 1 is a plan view showing a solar cell apparatus according to theembodiment, FIG. 2 is a sectional view showing a solar cell, FIG. 3 is agraph showing the composition of group I elements as a function of aheight in a light absorbing layer, and FIG. 4 is a sectional view takenalong line A-A′ of FIG. 1.

Referring to FIGS. 1 to 4, the solar cell apparatus according to theembodiment includes a support substrate 10, a plurality of solar cellsC1, C2, . . . , and CN, and a plurality of connection members 21, 22, .. . , and N.

The support substrate 10 has a plate shape or a sheet shape. The supportsubstrate 10 supports the solar cells C1, C2, . . . , and CN. Thesupport substrate 10 is an insulator. The support substrate 10 may beflexible. In addition, the support substrate 10 may be rigid.

For example, the support substrate 10 may include ethylene vinylacetate(EVA).

The solar cells C1, C2, . . . , and CN are provided on the supportsubstrate 10. The solar cells C1, C2, . . . , and CN are connected toeach other. In more detail, the solar cells C1, C2, . . . , and CN maybe connected to each other in series. The solar cells C1, C2, . . . ,and CN may be extended in one direction. In other words, the C1, C2, . .. , and CN may be arranged in the form of a stripe.

Each of the solar cells C1, C2, . . . , and CN may have a width W1 inthe range of about 0.5 cm to about 2.5 cm. In more detail, each of thesolar cells C1, C2, . . . , and CN may have the width W1 of about 0.8 cmto about 1.2 cm.

The solar cells C1, C2, . . . , and CN are overlapped with each other.In other words, the solar cells C1, C2, . . . , and CN are connected toeach other through the overlap region therebetween. In this case, eachoverlap region between the solar cells C1, C2, . . . , and CN may have awidth W2 in the range of about 1 mm to about 5 mm.

The connection members 21, 22, . . . , and N connect the solar cells C1,C2, . . . , and CN to each other. For example, the connection members21, 22, . . . , and N connect the solar cells C1, C2, . . . , and CN,which are overlapped with each other, to each other. In more detail, theconnection members 21, 22, . . . , and N may be interposed between thesolar cells C1, C2, . . . , and CN which are overlapped with each other.

Widths of the connection members 21, 22, . . . , and N may be equal tothe widths W2 of the overlap regions between the solar cells C1, C2, . .. , and CN. In addition, the connection members 21, 22, . . . , and Nmay cover the whole bottom surface of the solar cells C1, C2, . . . ,and CN. Each of the connection members 21, 22, . . . , and N has athickness in the range of about 20 μm to about 500 μm.

The connection members 21, 22, . . . , and N may include conductivepolymer. In more detail, the connection members 21, 22, . . . , and Nmay include anthracene conductive polymer, polyaniline conductivepolymer, or poly(ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)-based conductive polymer.

Therefore, the connection members 21, 22, . . . , and N may have highadhesive properties with respect to group I elements and conductiveoxide constituting the solar cells C1, C2, . . . , and CN. In addition,a material constituting the connection members 21, 22, . . . , and N mayeasily connect the solar cells C1, C2, . . . , and CN to each other evenin a low-temperature process.

In particular, since the conductive polymer constituting the connectionmembers 21, 22, . . . , and N has high corrosion resistance, the solarcells C1, C2, . . . , and CN can be prevented from being shorted witheach other. The conductive polymer allows the solar cells C1, C2, . . ., and CN to easily adhere to each other in a low-temperature process. Inaddition, since the conductive polymer has elasticity and a lowerthermal expansion coefficient, the solar cells C1, C2, . . . , and CNcan be prevented from being shorted with each other due to the thermalexpansion. The conductive polymer can bond the solar cells C1, C2, . . ., and CN with each other while representing improved adhesive strength.

As shown in FIG. 2, each of the solar cells C1, C2, . . . , and CNincludes a back electrode substrate 100, a light absorbing layer 200, abuffer layer 300, a high resistance buffer layer 400, and a window layer500.

The back electrode substrate 100 has a plate shape, and supports thelight absorbing layer 200, the buffer layer 300, the high resistancebuffer layer 400, and the window layer 500.

The back electrode substrate 100 is a conductor. In other words, theback electrode substrate 100 is a conductive substrate. The backelectrode substrate 100 may be flexible.

The back electrode substrate 100 includes group I elements. In otherwords, for example, the back electrode substrate 100 may include group Ielements such as copper (Cu) or silver (Ag).

In more detail, the back electrode substrate 100 may include group Ielements. In detail, the back electrode substrate 100 may include Cu orAg. In more detail, the back electrode substrate 100 may made of Cu orAg.

A thickness of the back electrode substrate 100 may be in the range ofabout 100 μm to about 15 mm. In detail, the thickness of the backelectrode substrate 100 may be in the range of about 300 μm to about 5mm.

The light absorbing layer 200 is provided on the back electrodesubstrate 100. The light absorbing layer 200 includes a group I element.In detail, the light absorbing layer 200 includes the compound of thegroup I element. In more detail, the light absorbing layer 200 includesa group I-III-VI-based compound. In more detail, the light absorbinglayer 200 may be made of a group I-III-VI-based compound.

For example, the group I-III-VI-based compound may include a Cu— --based compound selected from the group consisting of aCu—In—Ga—Se-based compound, a Cu—In—Se-based compound, a Cu—Ga—Se-basedcompound, a Cu—In—Ga—S-based compound, a Cu—In—S-based compound, aCu—Ga—S-based compound, and a Cu—In—Ga—Se—S-based compound, or aCu-III-VI-based compound selected from the group consisting of aCu—In—Ga—Se-based compound, a Cu—In—Se-based compound, aCu—Ga—Se-based-compound, a Cu—In—Ga—S-based compound, a Cu—In—S-basedcompound, a Cu—Ga—S-based compound, and a Cu—In—Ga—Se—S-based compound.

The composition of the group I element constituting the light absorbinglayer 200 may vary depending on the position of the light absorbinglayer 200. In more detail, the composition of the group I elementsconstituting the light absorbing layer 200 may be more increased in adirection toward the back electrode substrate 100. In addition, thecomposition of the group I elements constituting the light absorbinglayer 200 may be more reduced in the direction away from the backelectrode substrate 100.

In other words, as a height of the light absorbing layer 200 isincreased, the light absorbing layer 200 has the lower composition of agroup I element. In addition, as the height of the light absorbing layer200 is reduced, the light absorbing layer 200 has the higher compositionof the group I element.

In detail, the light absorbing layer 200 may include a first regionadjacent to the back electrode substrate 100, and a second region formedon the first region. The first region includes a group I-III-VI-basedcompound having the high composition of a group I element, and thesecond region includes a group I-III-VI-based compound having thecomposition of the group I element lower than the composition of thegroup I elements of the first region.

In addition, a group I-III-VI-based compound constituting the lower mostsurface of the light absorbing layer 200 includes the group I elementrepresenting the highest composition. In addition, a groupI-III-VI-based compound constituting the upper most surface of the lightabsorbing layer 200 includes the group I element representing the lowestcomposition.

For example, the back electrode substrate 100 includes Cu, and the lightabsorbing layer 200 may include a Cu-III-VI-based compound such as aCu—In—Ga—Se-based compound, a Cu—In—Se-based compound, a Cu—Ga—Se-basedcompound, a Cu—In—Ga—S-based compound, a Cu—In—S-based compound, aCu—Ga—S-based compound, or a Cu—In—Ga—Se—S-based compound. In moredetail, the Cu-III-VI-based compound can be represented as followingformulas.

Formula 1: Cu_(x)(In, Ga)ySe_(2z)

Formula 2: Cu_(x)In_(Y)Se_(2z)

Formula 3: Cu_(x)Ga_(Y)Se_(2z)

Formula 4: Cu_(x)(In, Ga)_(Y)S_(2z)

Formula 5: Cu_(x)In_(Y)S_(2z)

Formula 6: Cu_(x)Ga_(Y)S_(2z)

Formula 7: Cu_(x)(In,Ga)_(Y)(Se,S)_(2z)

In the above formulas, the X, Y, and Z are greater than 0 and less than2.

In this case, as shown in FIG. 3, the light absorbing layer 200 includesa Cu-III-VI-based compound having the high X in the direction toward theback electrode substrate 100. In contrast, the light absorbing layer 200includes a Cu-III-VI-based compound having the low X in the directionaway from the back electrode substrate 100.

In other words, the X of the Cu-III-VI-based compound may be graduallylowered in the direction away from the back electrode substrate 100.

For example, a value (A) of the X at the interfacial surface between theback electrode substrate 100 and the light absorbing layer 200 may be inthe range of about 0.9 to about 1.5. In addition, a value (B) of the Xat the interfacial surface between the light absorbing layer 200 and thebuffer layer 300 may be in the range of about 0.5 to about 0.95.

Therefore, the light absorbing layer 200 may include a Cu-III-VI-basedcompound having the highest Ag composition at the interfacial surfacewith the back electrode substrate 100. In addition, the light absorbinglayer 200 may include a Cu-III-VI-based compound having the lowest Cucomposition at the interfacial surface with the buffer layer 300.

The buffer layer 300 is provided on the light absorbing layer 200. Thebuffer layer 300 includes cadmium sulfide, and the energy band gap ofthe buffer layer 300 is in the range of about 2.2 eV to about 2.4 eV.

The high resistance buffer 400 is provided on the buffer layer 300. Thebuffer layer 400 includes a zinc oxide (i-ZnO) which is not doped withimpurities. The energy band gap of the high resistance buffer layer 400is in the range of about 3.1 eV to about 3.3 eV.

The window layer 500 is provided on the high resistance buffer layer400. The window layer 500 is transparent, and includes a conductivelayer. The window layer 500 may include a transparent conductive oxide.For example, the material of the window layer 500 may include Al dopedZnO (AZO).

Since the back electrode substrate 100 includes a group I element suchas Ag or Cu, the back electrode substrate 100 has low resistance. Inparticular, the back electrode substrate 100 has lower resistance andrepresents improved electrical characteristics as compared with anelectrode including Mo.

In addition, in the light absorbing layer 200, the composition of thegroup I element of the group I-III-VI-based compounds may vary with thepositions of the light absorbing layer 200, so that the optimalphotoelectric transformation efficiency can be represented.

In addition, the light absorbing layer 200 may include a groupI-III-VI-based compound having the high composition of the group Ielement in the direction toward the back electrode substrate 100.

Therefore, the solar cells C1, C2, . . . , and CN may include the lightabsorbing layer 200 which represents lower energy band gap toward theback electrode substrate 100. Accordingly, the light absorbing layer 200can effectively convert the sun light into electrical energy.

In addition, the back electrode substrate 100 may be flexible, and thesolar cells C1, C2, . . . , and CN may flexible over all.

As shown in FIG. 4, the solar cells C1, C2, . . . , and CN areoverlapped with each other. In more detail, the solar cells C1, C2, . .. , and CN adjacent to each other are partially overlapped with eachother. In other words, the solar cells C1, C2, . . . , and CN areconnected to each other while being overlapped with each other.

For example, a portion of the first solar cell C1 is overlapped with anupper portion of the second solar cell C2. In other words, the upperportion of the second solar cell C2 is interposed between the supportsubstrate 10 and the solar cell C1. In other words, the upper portion ofthe second solar cell C2 is inserted into the support substrate 10 andthe first solar cell C1. In addition, a top surface of the second solarcell C2 is connected to a bottom surface of the first solar cell C1.

In more detail, the first solar cell C1 includes a first back electrodesubstrate 110, a first light absorbing layer 210, a first buffer layer310, a first high resistance buffer layer 410, and a first window layer510 that are sequentially stacked on each other. In addition, the secondcell C2 includes a second back electrode substrate 120, a second lightabsorbing layer 220, a second buffer layer 320, a second high resistancebuffer layer 420, and a second window layer 520 which are sequentiallystacked on each other.

In this case, a portion of the first back electrode substrate 100 isbent and provided on the second window layer 520. A bottom surface ofthe first back electrode substrate 110 is connected to a top surface ofthe second window layer 520.

The first connection member 21 is interposed between the bottom surfaceof the first back electrode substrate 110 and the top surface of thesecond window layer 520. The first back electrode substrate 110 isconnected to the second window layer 520 through the first connectionmember 21. In other words, the first connection member 21 directly makescontact with the bottom surface of the firs back electrode substrate 110and the top surface of the second window layer 520.

As described above, the first connection member 21 may includeconductive polymer. In addition, the first connection member 21 mayinclude a conductor, solder paste, or a conductive tape.

In addition, the first connection member 21 may be formed through thefollowing processes.

In order to form the first connection member 21, conductive polymer iscoated on the bottom surface of the first back electrode substrate 110and/or the second window layer 520. In more detail, the conductivepolymer may be coated corresponding to the overlap region between thefirst and second solar cells C1 and C2.

Thereafter, the first and second solar cells C1 and C2 may be overlappedwith each other, and may be bonded with each other through thermalcompression. Therefore, the first connection member 21 includingconductive polymer may be formed between the first and second solarcells C1 and C2.

As described above, since the first connection member 21 includesconductive polymer, the first connection member 21 may be easily formedthrough a simple process such as a coating scheme or a thermalcompression scheme.

Since the first connection member 21 includes conductive polymer, thefirst connection member 21 may be effectively bonded to the first backelectrode substrate 110 and the second window layer 520.

Therefore, the first connection member 21 is effectively bonded to thefirst back electrode substrate 110 and the second window layer 520, sothat the first and second solar cells C1 and C2 are effectivelyconnected to each other physically and electrically.

In addition, the bottom surface of the first back electrode substrate110 can be connected to the top surface of the second window layer 520through the direct contact with the top surface of the second windowlayer 520.

In addition, a portion of the second solar cell C2 is overlapped withthe third solar cell C3. In other words, a portion of the third solarcell C3 is interposed between the support substrate 10 and the secondsolar cell C2. In other words, a portion of the third solar cell C3 isinserted between the support substrate 10 and the second solar cell C2.In addition, the top surface of the third solar cell C3 is connected tothe bottom surface of the second solar cell C2.

In detail, the third solar cell C3 includes a third back electrodesubstrate 130, a third light absorbing layer 230, a third buffer layer330, a third high resistance buffer layer 430, and a third window layer530 that are sequentially stacked on each other.

In this case, the portion of the second back electrode substrate 120 isbended and provided on the third window layer 530. A bottom surface ofthe second back electrode substrate 120 is connected to the top surfaceof the third window layer 530.

In addition, the second connection member 22 is interposed between thebottom surface of the second back electrode substrate 120 and the topsurface of the third window layer 530. The second back electrodesubstrate 120 is connected to the third window layer 530 through thesecond connection member 22. In other words, the second connectionmember 22 directly makes contact with the bottom surface of the secondback electrode substrate 120 and the top surface of the third windowlayer 530.

The second connection member 22 may include a conductor, solder paste,or a conductive tape. Similarly to the first connection member 21, thesecond connection member 22 may include conductive polymer, and thesecond solar cell C2 and the third solar cell C3 are effectivelyconnected to each other through the second connection member 22.

In addition, the bottom surface of the second back electrode substrate120 may be connected to the top surface of the third window layer 530through the direct contact with the top surface of the window layer 530.

As described above, the solar cells C1, C2, . . . , and CN are connectedto each other while being overlapped with each other, and are connectedto each other in series.

Therefore, the solar cell apparatus according to the embodiment can bemanufactured without a patterning process to distinguish between thesolar cells C1, C2, . . . , and CN, and to connect the solar cells C1,C,. . . , and CN to each other.

Therefore, the solar cell apparatus according to the embodiment can beeasily manufactured.

In addition, in the solar cell apparatus according to the embodiment,the overlap region between the solar cells C1, C2,. . . , and CN can beminimized. In addition, the overlap region between the solar cells C1,C2, . . . , and CN can convert the sun light into the electrical energy.

For example, a portion of the solar cell C1 overlapped with the secondsolar cell C2 can convert the sun light into the electrical energy.

Therefore, the solar cell apparatus according to the embodimentrepresents improved power generation efficiency.

In addition, the solar cell apparatus according to the embodiment mayfurther include a protective substrate to cover the solar cells C1, C2,.. . , and CN. In this case, the protective substrate may be transparent,include an insulator, and be flexible. For example, the protectivesubstrate may include an ethylene-vinyl acetate film.

In addition, the solar cells C1, C2, . . . , and CN and the supportsubstrate 10 may be flexible. Therefore, the solar cell apparatusaccording to the embodiment may be flexible over all.

FIGS. 5 to 8 are sectional views showing a method for manufacturing thesolar cells. The above description about the solar cell apparatus willbe incorporated in the description about the method for manufacturingaccording to the present embodiment.

Referring to FIG. 5, the back electrode substrate 100 including thegroup I element is prepared.

Referring to FIG. 6, a preliminary light absorbing layer 201 is formedon the back electrode substrate 100.

The preliminary light absorbing layer 201 may include a group IIIelement or a group VI element. In more detail, the preliminary lightabsorbing layer 201 may include only a group III element. In moredetail, the preliminary light absorbing layer 201 may include group IIIelements and group VI elements.

In addition, the preliminary light absorbing layer 201 may include onelayer or a plurality of layers. In addition, a thickness of thepreliminary light absorbing layer may be in the range of about 100 nm toabout 1000 nm.

For example, the preliminary light absorbing layer 201 may include asingle layer including a group III-VI-based compound. In detail, thepreliminary light absorbing layer 201 may include an In—Se-basedcompound, an In—Ga—Se-based compound, a Ga—Se-based compound, anIn—S-based compound, an In—Ga—S-based compound, a Ga—S-based compound,or an In—Ga—Se—S-based compound.

The group III-VI-based compound may be deposited through a sputteringprocess. In other words, the preliminary light absorbing layer 201 maybe formed through a sputtering process using a sputtering targetincluding the group III-VI-based compound.

The preliminary light absorbing layer 201 may be formed through aco-evaporation scheme to deposit a group III element and a group VIelement while simultaneously evaporating the group III element and thegroup VI element.

In addition, the preliminary light absorbing layer 201 may be formed byprinting a paste including the group III-VI-based compound on the backelectrode substrate 100.

The preliminary light absorbing layer 201 may be formed by spraying asolution including the group III-VI-based compound on the back electrodesubstrate 100.

In addition, the preliminary light absorbing layer 201 may include onlythe group III element without the group VI element.

Referring to FIG. 7, after the preliminary light absorbing layer 201 hasbeen formed, heat treatment is performed for both of the back electrodesubstrate 100 and the preliminary light absorbing layer 201.

Therefore, the group I element constituting the back electrode substrate100 is spread into the preliminary light absorbing layer 201, and thegroup III-VI elements constituting the preliminary light absorbing layer201 are spread into a portion of the back electrode substrate 100.

In addition, the group I element constituting the back electrodesubstrate 100 reacts with the group III-VI-based compounds constitutingthe preliminary light absorbing layer 201, thereby forming a groupI-III-VI-based compound.

Therefore, the light absorbing layer 200 including the groupI-III-VI-based compound is formed on the back electrode substrate 100.

The heat treatment process is performed in the temperature of about 300°C. to about 650° C. for about 5 min to about 60 min.

Referring to FIG. 8, a cadmium sulfide is deposited on the lightabsorbing layer 200 to form the buffer layer 300. Thereafter, a zincoxide is deposited on the buffer layer 300 to form the high resistancebuffer layer 400.

Thereafter, Al doped ZnO is deposited on the high resistance bufferlayer 400 to form the window layer 500.

According to the method for manufacturing the solar cell of theembodiment, a process of depositing a group I element such as Ag or Cuis not required to form the light absorbing layer 200.

Therefore, the light absorbing layer 200 may be formed at a lowtemperature, and the solar cells C1, C2, . . . , and CN can be easilymanufactured.

The connection members 21, 22, . . . , and N are provided on one outerportion of the top surface of the solar cells C1, C2, . . . , and CN,and the solar cells C1, C2, . . . , and CN are connected to each otherto be overlapped with each other. Thereafter, the protective substrateand the support substrate 10 are bonded with the top and bottom surfacesof the solar cells C1, C2, . . . , and CN, respectively, therebymanufacturing the solar cell apparatus according to the embodiment.

As described above, the solar cell apparatus according to the embodimentcan be manufactured without the patterning process.

FIGS. 9 and 10 are sectional views showing a light absorbing layeraccording to another embodiment. The present embodiment will bedescribed by making reference to the description about the previousembodiment. Procedures of forming a preliminary light absorbing layerand a light absorbing layer will be additionally described. Thedescription about the previous embodiment will be incorporated in thedescription about the present embodiment except for the descriptionabout modifications.

Referring to FIG. 9, a preliminary light absorbing layer 202 is formedon the back electrode substrate 100. The preliminary light absorbinglayer 202 includes a group III element. In detail, the preliminary lightabsorbing layer 2 includes a group III element or a group III elementcompound.

In this case, the preliminary light absorbing layer 202 does not includea group VI element.

For example, the preliminary light absorbing layer 202 may include Inand/or Ga, or may include an Indium oxide or a Gallium oxide. Inaddition, the preliminary light absorbing layer 202 may include anIndium oxide layer or a gallium oxide layer.

Referring to FIG. 10, the preliminary light absorbing layer 202 and theback electrode substrate 100 are subject to heat treatment at theatmosphere of the group VI element such as Se, so that the lightabsorbing layer 200 is formed on the back electrode substrate 100. Thegroup I element constituting the back electrode substrate 100, the groupIII element constituting the preliminary light absorbing layer 201, andthe group VI element around the preliminary light absorbing layer 202react each other, so that the group I-III-VI compound is formed, therebyforming the light absorbing layer 200.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

INDUSTRIAL APPLICABILITY

The embodiment is applicable to a solar power generation field.

1. A solar cell apparatus comprising: a first solar cell; and a secondsolar cell partially overlapping with the first solar cell and connectedto the first solar cell.
 2. The solar cell apparatus of claim 1, whereinthe first solar cell comprises: a first conductive substrate; a firstlight absorbing layer on the first conductive substrate; and a firstwindow layer on the first light absorbing layer, wherein the secondsolar cell comprises: a second conductive substrate; a second lightabsorbing layer on the second conductive substrate; and a second windowlayer on the second light absorbing layer, and wherein a bottom surfaceof the first conductive substrate makes contact with a top surface ofthe second window layer.
 3. The solar cell apparatus of claim 2, whereinthe first conductive substrate includes a group I element, and the firstlight absorbing layer includes the group I element, a group III element,and a group VI element.
 4. The solar cell apparatus of claim 3, whereina composition of the group I element in the first light absorbing layeris gradually increased in a direction toward the first conductivesubstrate.
 5. The solar cell apparatus of claim 3, wherein the group Ielement includes silver (Ag) or copper (Cu).
 6. The solar cell apparatusof claim 1, further comprising a connection member interposed betweenthe first and second solar cells to connect the first solar cell to thesecond solar cell.
 7. The solar cell apparatus of claim 6, wherein theconnection member includes conductive polymer.
 8. The solar cellapparatus of claim 6, wherein a width of the first solar cell is in arange of about 0.8 cm to about 1.2 cm, and a width of the connectionmember is in a range of about 20 μm to about 500 μm.
 9. The solar cellapparatus of claim 1, further comprising a support substrate attached tolower portions of the first and second solar cells.
 10. The solar cellapparatus of claim 9, wherein the support substrate is flexible.
 11. Asolar cell apparatus comprising: an insulating substrate; a first solarcell on the insulating substrate; and a second solar cell having aportion interposed between the insulating substrate and the first solarcell while being connected to a bottom surface of the first solar cell.12. The solar cell apparatus of claim 11, further comprising aconnection member interposed between the bottom surface of the firstsolar cell and a top surface of the second solar cell while directlymaking contact with the bottom surface of the first solar cell and thetop surface of the second solar cell.
 13. The solar cell apparatus ofclaim 11, further comprising a protective substrate to cover the firstand second solar cells.
 14. The solar cell apparatus of claim 13,wherein the insulating substrate, the first solar cell, the second solarcell, and the protective substrate are flexible.
 15. A solar cellapparatus comprising: a first solar cell; a second solar cell connectedto the first solar cell; and a connection member connecting the firstsolar cell to the second solar cell, wherein the connection memberincludes conductive polymer.
 16. The solar cell apparatus of claim 15,wherein the first solar cell includes a conductive substrate including agroup I element, the second solar cell includes a window layer includinga transparent conductive oxide, and the connection member directly makescontact with the conductive substrate and the window layer.
 17. Thesolar cell apparatus of claim 16, wherein the conductive substrateincludes copper (Cu) or silver (Ag), and the window layer includes azinc oxide.
 18. The solar cell apparatus of claim 15, wherein the firstand second solar cells are overlapped with each other, and theconnection member directly makes contact with a bottom surface of thefirst solar cell and a top surface of the second solar cell.
 19. Thesolar cell apparatus of claim 15, wherein the conductive polymerincludes anthracene conductive polymer, polyaniline conductive polymer,or poly(ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)-based conductive polymer.
 20. The solar cell apparatus ofclaim 15, wherein the connection member has elasticity.